European Journal of Obstetrics & Gynecology and Reproductive Biology
Ultrasonographic cervical length measurement at 10–14 and 20–24 weeks gestation and the risk of preterm delivery
Introduction
Preterm delivery, defined as delivery before 37 weeks of gestation, is associated with a 15–20% mortality rate and remains responsible for 75% of perinatal deaths in foetuses without anomalies [1]. The accurate diagnosis and prediction of preterm delivery remains a major problem in obstetrics. There is no consensus regarding the evaluation of cervical length during pregnancy for predicting preterm delivery, which may be explained by differences in study populations (low- or high-risk patients), the ratio of primigravidas to multigravidas, the type of investigation (longitudinal or cross-sectional), gestational age at ultrasonographic examination, and racial factors. Several studies consistently found that the shorter the cervical length, the higher the rate of spontaneous preterm delivery [2], [3], [4], [5]. Ultrasonographic assessment of cervical length is becoming an increasingly popular component of prenatal care. However, the role of this method as a screening tool in the prediction of preterm delivery in the first or early second trimester of pregnancy is still controversial [6], [7], [8], [9], [10], [11].
It is important to identify the patients at risk for preterm delivery to avoid unnecessary treatments, such as cerclage, corticosteroids, and antibiotics. Therefore, we investigated whether cervical length in the first trimester (10–14 weeks) predicts spontaneous preterm delivery longitudinally by comparing this measurement with that obtained in the second trimester (20–24 weeks) in an asymptomatic population of singleton pregnancies.
Section snippets
Materials and methods
We conducted this prospective study involving 152 asymptomatic women with singleton pregnancies at our university clinic between February 2003 and November 2004. The ethics committee of our university hospital approved the study and informed consent was obtained from the patients. As part of the routine antenatal care, transabdominal ultrasonography was performed initially, followed by transvaginal ultrasonography to measure cervical length using a real-time 6 MHz curvilinear transvaginal probe
Statistical analysis
A receiver operating characteristic (ROC) curve was constructed for cervical lengths to test the effectiveness of various cutoff points in predicting premature delivery. The areas under the ROC curves were calculated and the sensitivity, specificity, and positive-predictive value (PPV) for the cervical length of the most appropriate cutoff point were calculated for predicting preterm delivery [12]. Cervical length measurements were expressed as the mean ± standard deviation (S.D.). Student's t
Results
One hundred and fifty-two singleton pregnancies met the inclusion criteria during the study period. The mean age (±S.D.) of the preterm and term groups was 27.8 ± 6.9 and 26.0 ± 5.5 years (P = 0.184), respectively. There were no statistically significant differences in previous preterm deliveries, previous miscarriages, education level, parity, or whether the patient was a cigarette smoker between the group that delivered at term and the preterm group. Spontaneous preterm delivery before 35 weeks
Discussion
Unlike most studies that made single measurements, we measured cervical length at 10–14 and at 20–24 weeks gestation in an asymptomatic population of pregnant women. We found an association with the cervical length at 20–24 weeks, which was more predictive, whereas this association was not found at 10–14 weeks gestation. The risk of preterm delivery was higher in pregnant women whose cervical length decreased rapidly from the first to the second scan.
In unselected low-risk asymptomatic
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